1. Field of the Invention
The present invention relates to a feed pump attached to a fuel injection pump applied to, for example, a diesel engine.
2. Description of the Related Art
There is, as a prior art, for example, a fuel injection pump described below.
The fuel injection pump is provided with a feed pump that draws fuel from a fuel tank and supplies the same to an injection pump main body.
As shown in FIG. 4, the feed pump is composed of a pump element 110 rotated by a driving shaft 100, a pump plate 120 disposed at one end side of the pump element 110 in the axial direction thereof, and a pump cover 130 that covers the other end side of the pump element 110 in the axial direction thereof and an outer periphery of the pump element in the radial direction thereof, and that is combined with the pump plate 120 in a liquid-tight manner; and is fastened to a housing 140 of the injection pump main body by bolts.
The pump element 110 is a trochoid-type pump in which an inner gear 112 having outer teeth is disposed inside an outer gear 111 having inner teeth.
As shown in FIG. 5, in the pump plate 120, a shaft hole 121, through which the driving shaft 100 is inserted, is formed at the center of the plate, and an inlet port 122 and an outlet port 123 that are shaped like an arc are formed around the shaft hole 121. Further, bolt holes 124 and positioning holes 125 are formed on the outer periphery of the pump plate 120.
The pump cover 130 has an outer shape identical to that of the pump plate 120. In the cover, bolt holes and positioning holes are formed in a manner similar to the pump plate 120.
The above-described feed pump is fastened to the housing 140 by inserting a bolt (not shown) into each bolt hole 124 of the pump plate 120 and the pump cover 130, and threading the bolt into a threaded hole (not shown) formed in a side face of the housing 140. At this time, as shown in FIG. 4, the center of the pump plate 120 is sometimes deformed toward-the pump element 110. As a result, there is a possibility that the drawbacks (1), (2) described below may be caused.
(1) A thrust clearance between the pump plate 120 and the pump element 110 is reduced, so that seizing occurs.
(2) Leakage of fuel occurs at the deformed portion of the pump plate 120, so that a low-speed discharging property is reduced.
The deformation of the center of the pump plate 120 is caused by the reduction of rigidity of the pump plate 120 because of the large (long) inlet port 122 and outlet port 123 that are formed around the shaft hole 121 in the circumferential direction of the shaft hole. Therefore, the increase of the thickness of the pump plate to increase the rigidity of the pump plate 120 can be taken into consideration. However, in this case, demerits such as the increase of material cost, the increase of the size of the pump and the reduction of workability in pressing, occur. Accordingly, a method that causes the thickness of the pump plate 120 to be increased is not required.